fix: improve arrow function parsing in getParams

- Fixed regex to properly convert arrow functions without braces
- Handles both block and expression arrow functions correctly
- Fixes 'SyntaxError: Unexpected token' when parsing arrow functions
- async () => expr now converts to async function() { return expr }

This resolves parser errors that were preventing proper function
parameter extraction from arrow functions in BDD tests.

Author: kobenguyent

lib/parser.js

@@ -19,11 +19,15 @@ function getParams(fn) {
   try {
     // Convert arrow functions to regular functions for parsing
     let fnString = fn.toString()
-    // Handle async arrow functions: async (...) => { becomes async function(...) {
-    fnString = fnString.replace(/^async\s*(\([^)]*\))\s*=>/, 'async function$1')
-    // Handle regular arrow functions: (...) => { becomes function(...) {
-    fnString = fnString.replace(/^(\([^)]*\))\s*=>/, 'function$1')
-    
+    // Handle async arrow functions: async (...) => expr becomes async function(...) { return expr }
+    // Handle async arrow functions: async (...) => { ... } becomes async function(...) { ... }
+    fnString = fnString.replace(/^async\s*(\([^)]*\))\s*=>\s*\{/, 'async function$1 {')
+    fnString = fnString.replace(/^async\s*(\([^)]*\))\s*=>\s*(.+)$/, 'async function$1 { return $2 }')
+    // Handle regular arrow functions: (...) => expr becomes function(...) { return expr }
+    // Handle regular arrow functions: (...) => { ... } becomes function(...) { ... }
+    fnString = fnString.replace(/^(\([^)]*\))\s*=>\s*\{/, 'function$1 {')
+    fnString = fnString.replace(/^(\([^)]*\))\s*=>\s*(.+)$/, 'function$1 { return $2 }')
+
     const reflected = parser.parse(fnString)
     if (reflected.args.length > 1 || reflected.args[0] === 'I') {
       output.error('Error: old CodeceptJS v2 format detected. Upgrade your project to the new format -> https://bit.ly/codecept3Up')